Circa.
1300 to 1600
1800-1920
If you are referring to 'c1946', it means circa; when referring to dates it means approximately, on or about, around that time...
If you are referring to dates, its: AD from Latin Anno Domini (meaning year of our Lord). Recently it has become frequent for secular literature to substitute CE from English Common Era.
Audacious derives from the Latin word audax, meaning "brave, daring". When declined, this Latin adjective took the form audac-.Audacious has been in the English language since at least 1550. Audacity dates back to at least 1450.
Important dates were marked in red ink during the Roman Republic. The meaning is still the same, although it's also commonly used to indicate more personal red letter days.
1946 to 1954
Latin Pulse - 2006 was released on: USA: 2006
7 September 1533 - 24 March 1603
1955 to 1975
Latin Access - 2002 was released on: USA: January 2002
In the Latin Quarter - 1915 was released on: USA: 2 January 1915